Fluid filters are commonly used in engine lubrication systems, hydraulic systems, and fuel systems to remove solid materials, such as dirt and abrasives, from the fluid being circulated. Traditionally, fluid filters include a filtering member or element disposed within a main body, casing, or housing. A tapping plate or cover is fastened to the main body to enclose the filtering member. The tapping plate includes a plurality of openings to enable fluid flow through the filtering member. The fluid flow may be either directed into the filter through a central opening in the tapping plate or through a plurality of circumferential openings disposed radially about the tapping plate. The fluid filter is typically mounted to the engine or hydraulic system by spinning the tapping plate onto a filter mount extending from the engine or hydraulic system. This type of mounting method is commonly known as a spin-on type.
A uniquely shaped primary sealing element or gasket traditionally extends from the exterior of the tapping plate to seal a volume between the tapping plate and the filter mount. Depending on the specific design of the engine or hydraulic system, the sealing element may be positioned in either an inboard position or an outboard position relative to the main body diameter. The unique shapes of these specialized gaskets are used to enable the gaskets to be more readily secured to the tapping plate. Uniquely formed gaskets, such as those shown in U.S. Pat. Nos. 4,834,885 and 4,969,994, have the distinct disadvantage of requiring special manufacturing techniques to produce. These special manufacturing techniques almost inherently require added costs.
Alternatively, die casted tapping plates are occasionally used. These die casted tapping plates normally include specialized seal retaining means for retaining lathe-cut gaskets. Lathe-cut gaskets are more readily and economically produced relative to the specialized gasket described above. However, die casted tapping plates are generally more expensive to tool and manufacture relative to stamp-formed tapping plates. Some prior art designs have attempted to combine a stamp-formed cover with a steel baseplate to be used as a tapping plate assembly. The gasket is retained in the cover and the cover is welded to the baseplate for added rigidity. An example of this combination design is shown in U.S. Pat. No. 5,490,930. However, it should be appreciated that this design requires additional parts and processing steps, which inherently increases the cost of manufacturing.
A second seal is commonly used to prevent fluid flow between the tapping plate and the main body. An example of this second seal design is shown in U.S. Pat. No. 4,369,113. The second seal is typically secured in place by a series of metal folds or double-rolls formed in the main body and the tapping plate. Although this arrangement appears to be temporarily effective, it may not afford maximum leakage protection during severe operating conditions. Specifically, it is believed that the two-seal design may fail to prevent fluid leakage when exposed to hydrostatic pressure or hydrodynamic impulses. Such severe operating conditions commonly occur in industrial or heavy-equipment applications, but may also occur in passenger car applications.
Metal folds are also commonly used for joining and sealing the main body to the tapping plate. More particularly, a free end of the tapping plate is rolled or crimped together with a free end of the main body. The combination is typically rolled twice and crimped to form a bead around the edge of the filter assembly. Although this method also appears to be temporarily effective, it is not believed to afford maximum leakage protection during severe conditions. Similar to the two-seal design, the double-rolled bead may fail to prevent fluid leakage when exposed to hydrostatic pressure or hydrodynamic impulses. Moreover, the double-rolled seam is relatively expensive to manufacture and may require seam assembly control and/or additional sealing compounds to produce a reliable interconnection, as variations in seam integrity and welding may occur. Sealing compounds are typically applied during manufacturing to limit fluid leakage through the main body and tapping plate interconnection.
Accordingly, there exists a need in the relevant art to provide a spin-on fluid filter having a tapping plate capable of effectively retaining an economical lathe-cut gasket, rather than a more expensive uniquely-formed gasket. Furthermore, there exists a need in the relevant art to provide a stamp-formed tapping plate capable of retaining the lathe-cut gasket.